12.1 The acid in the stomach destroys microbes.
12.2 The skin prevents microbes from getting into the body.
12.3 Sticky mucus in the lungs nets microbes, and then cilia span it out of the lungs
13. D. Skin
14. False - Mucos prevents microbes in certain organs
15. False - It is a colorless fluid.
16. A. Bacteria
17. B1
8. False - Thymus in the anterior part of the chest directly behind the sternum between the lungs
19. C. Red blood cells
20. False - Bone marrow produces the known blood cells
21. True
22. False - It starts in the bone marrow.
23. True
1. The correct answer is a.
Neurons communicate using action potentials, that travel down neurons using an electrochemical cascade. These action potentials are mediated by changes in the polarity of the cell membrane. At the beginning of the action potential, the Na+ channels open and this causes an influx of Na+ into the nerve cell, triggering, in turn, the depolarization of the membrane.
2. The correct answer is b.
The Krebs cycle (also known as the citric acid cycle) is a process involved in cellular respiration. The Krebs cycle happens in the mitochondria and involves the transformation of Acetyl coA to molecules, that will then be used to create ATP (the energy molecule). Acetyl coA goes through several chemical transformations and the energy released is transferred to NAD and FAD. In a process before the Krebs cycle, Pyruvate (produced by glycolysis) forms the acetyl coA. Therefore, pyruvate does not intervene in the Krebs cycle.
3. The correct answer is b.
The neuromuscular junction is a chemical synapse connecting a motor neuron and a muscle fiber. The signal transmitted from the motor neuron to the muscle fiber triggers the muscle contraction. The process is mediated partly through ion channel linked receptors. When acetylcholine (the ligand) binds to the receptor, the ion channel part of the receptor opens and this produces an influx of ions intracellularly.
4. The correct answer is c.
Cystic fibrosis is a inherited disorder that affects mostly the lungs, but also other organs of the body, such as the liver and the pancreas. It is caused by a mutation in the CTFR gene. This gene encodes a protein that is a chloride ion channel and is responsible for the movement of water in and out of the cells. The mutations in this gene result in a disruption of this ion channel, causing a change in the consistency of the mucus and sweat produced by the organism.
5. The correct answer is d.
The CTFR protein (the product of the CTFR gene) is a chloride ion channel regulated by cAMP. This ion channel is activated by phosphorylation, caused by cAMP - dependent protein kinase (PKA). PKA needs to bind two cAMP in order to be activated and able to phosphorylate other proteins.
Carbohydrates are one of the four classes of organic molecules in living organisms. There are two types of carbohydrates namely the simple and complex. Simple which is also called simple sugar is found in white sugar and in fruits and milk. On the other hand, complex also called starches are in grain products. Examples of it would be bread, rice and pasta.
Gender
Skin pigmentation
Religiously
Preference of opposite sex
Mental challenges
Physical challenges
Weight
Age
Hope these helped. :)
